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Three-body force effect on the properties of asymmetric nuclear matter
Wei ZuoInstitute of Modern Physics, Lanzhou, China
Properties of ANM
Neutron star structure
Properties of neutron-rich nuclei and heavy nuclei
Isospin transport in HIC
Effective NN interaction in nuclear medium
Neutron star cooling
Nuclear many-body model
Theoretical Approaches
• Skyrme-Hartree-Fock• Relativistic Mean Field Theory• Relativistic Hartree-Fock
• Variational Approach• Green’s Function Theory • Brueckner Theory• Dirac-Brueckner Approach• Effective Field Theory
Bethe-Goldstone Theory
Bethe-Goldstone equation and effective G-matrix
→ is the realistic nucleon-nucleon interaction. In our calculation:
★ Two-body interaction : AV18 (isospin dependent)
★ Effective three-body force
→ Pauli operator :
→ Single particle energy :
→ “Auxiliary” potential : continuous choice
);,()()(
),();,(
21 21
212121
Gikk
kkkkQkkvvG
kkNNNN
Ak
kkkkGkkknkU ')]'()(['Re)'()('
Nuclear Matter Saturation Problem
The model of rigid nucleons interacting via realistic two-body forces fitting in-vacuum nucleon-nucleon scattering data can not reproduce the empirical saturation properties of nuclear matter (Coestor band, Coestor et al., PRC1(1970)765)
Effective NN interaction
Dirac-Brueckner approach [R.Machleidt, Adv. Nucl. Phys. 16 (1989) 189; Serot andWalecka, Int. Journ. Mod. Phys. E6(1997) 515]
There are on the market different ways on how to introduce the medium effects:
◆ Phenomenologocal three-body forceR
ijkijkijk VVV 2
--- Two or few adjustable parameters, which are adjusted simultaneously on nuclear saturation point and light nuclei (3He)properties.--- Extensively applied to neutron star physics within both variational approach [Wiringa et al., PRC38(1988) 1010; Akmal et al., PRC56 (1997)2261; C58(98) 1804.] and BHF approach [Baldo et al., Astron. Astrophys. 328(1997) 274.]
◆ Microscopic three-body force
At the lowest mean field approximation, two problems of BHF approach for predicting nuclear s.p. properties:
1. At densities around the saturation density, the predicted optical potential depth is too deep as compared to the empirical value, and it destroy the Hugenholtz-Van Hove (HVH) theorem.
Solution: to include the effect of ground state correlations
J. P. Jeukenne et al., Phys. Rep. 25 (1976) 83
M. Baldo et al., Phys. Lett. 209 (1988) 135; 215 (1988) 19
2. At high densities, the predicted potential is too attractive and its momentum dependence turns out to be too weak for describing the experimental elliptic flow data.
P. Danielewicz, Nucl. Phys. A673 (2000) 375
Improvement in three aspects:
1. Extend the calculation of the effect of ground state correlations to asymmetric nuclear matter
Zuo, Bombaci, Lombardo, PRC 60 (1999) 024605
2. Include a microscopic three-body force (TBF) in the BHF calculation
Zuo, Lejeune, Lombardo, Mothiot, NPA706 (2002) 418; EPJA 14(2002)469;
Z. H. Li et al., PRC 77 (2008) 034316
3. The TBF-induced rearrangement contribution for calculating the s.p. properties in Bruckner theory
W. Zuo et al., PRC72 (2005)014005; PRC74 (2006) 014317
Microscopic Three-body Forces
N
R ,
,
)(b )(c
N
N
N
N
N
N
N
, , , ,
N
N
,
,
R,
)(a
,
, ,
Z-diagram
• Based on meson exchange approach• Be constructed in a consistent way with the adopted two-body force ----- microscopic
TBF !
Grange et al., PRC40(1989)1040
Effective Microscopic Three-body Force
Effective three-body force
→ Defect function:
★ Short-range nucleon correlations (Ladder correlations)
★ Evaluated self-consistently at each iteration
Effective TBF ---- Density dependent Effective TBF ---- Isospin dependent for asymmetric nuclear matter
W. Zuo, A. Lejeune, U.Lombardo, J.F.Mothiot, NPA706(2002)418
EOS of SNM & saturation properties
r (fm-3) EA (MeV) K (MeV)
0.19 –15.0 210
0.26 –18.0 230
Saturation properties:
TBF is necessary for reproducing the empirical saturation property of nuclear matter in a non-relativistic microscopic framework.
W. Zuo, A. Lejeune, U.Lombardo, J.F.Mothiot, Nucl.Phys.A706(2002)418 W. Zuo et al., Phys. Rev. C69 (2004) 064001
2
2
( , , ) ( , ,0) ( , )
Parabolic law : linear dependence on
A A symE T E T E T
Isospin dependence of the EOS
Bombaci, Lombardo, PRC 44 (1991) 1892Zuo, bombarci, Lombardo, PRC 60 (1999) 024605
Density dependence of symmetry energy: Slope parameter around saturation density
Neutron skin thickness
Surface symmetry energy
Nuclear mass
Isospin diffusion & isoscaling
Pymgy dipole resonance
IVGQR
β-decay energy of heavy nuclei
Microscopic predictions
Experimental constraints:
Microscopic predictions:
Zuo, Bombaci, Lombardo, EPJA 50 (2014) 12
Density dependence of symmetry energy
TBF effect Thermal effect
Predictions from different ab. initio approaches
?
EOS of symmetric nuclear matterDensity dependence of symmetry energy
Single Particle Potential beyond the mean field approximation:
1. Single particle potential at lowest BHF level
eff3
TBF
1( )
2 i jij k A
Vk ij ij n n
n
'
( ) ( ') Re ' [ ( ) ( ')] 'BHF Ak
U k n k kk G k k kk
2. Ground state correlations
Full s.p. potential: 2( ) ( ) ( ) ( )BHF TBFU k U k U k U k
3. TBF rearrangement
Single particle properties in SNM (TBF effect and g.s. correlation effect)
Single particle potential Effective mass
Single particle potentials in ANM ( TBF contribution and the effect of g.s. correlations )
Lowest BHF approximation Pauli rearrangement contribution
TBF rearrangement contribution
TBF effect on Nucleon momentum distribution in ANM
At high densities well above the saturation density, the TBF lead to an enhancement of the depletion of nuclear Fermi sea.
YIN, li, Wang, and Zuo, Phys. Rev. 87 (2013) 014314
Wit
ho
ut
TB
F
Wit
h T
BF
TBF effect on nucleon superfluidity in neutron star matter
Dong, Lombardo and Zuo, PRC 87, 062801(R) (2013)
W. Zuo et al., PLB 595(2004)44
1S0 proton superfluidity in neutron star matter
3PF2 neutron superfluidity in neutron matter
1. TBF provides a repulsive contribution to the EOS of nuclear matter and improves remarkably
the predicted saturation properties.
2. TBF and thermal effect do not alter he empirical parabolic law fulfilled by the EOS of ANM.
3. TBF may lead to a strong enhancement of the stiffness of symmetry energy at high densities.
4. TBF induces a strongly repulsive and momentum-dependent rearrangement contribution to
the s.p. potential at high densities.
5. At high densities, TBF may lead to an enhancement of the depletion of nuclear Fermi sea.
Summary
Thank you for attention ! 谢谢大
家 !